What is the FAC file format?
A .fac file is a FaceSaver bitmap image - a raster portrait format created around 1985 for UNIX workstation face-directory databases. FaceSaver was a utility developed by Lou Katz at Metron Computerware for storing small employee or user photographs, typically at 64×96 pixels, in fingerd face databases and early internet mailing-list directories.
The format uses a text-prefixed structure: several ASCII key:value header lines (including PicData: and Image: fields, and optional personal metadata such as name, institution, and email) precede the image data. The bitmap is stored as ASCII hex-encoded scan lines in bottom-to-top, left-to-right order. This hex encoding makes the content human-inspectable but inflates file size relative to the actual pixel data. Color depth ranges from 1-bit monochrome to 8-bit grayscale; the original use case was black-and-white face portraits.
.fac is not to be confused with the XBM family of UNIX bitmap formats or with the separate X-Face format used to embed tiny face bitmaps inside email headers - both serve similar social-directory purposes but use incompatible encodings.
No modern software creates new .fac files. XnView and XnView MP can open them; the command-line tool fromface was the canonical UNIX utility for extracting images from FaceSaver databases. The format is obsolete, replaced by PNG and JPEG for portrait storage.
Security & safety
RISK: LOWFAC is a plain text+hex format; it cannot execute code. No known malware exploits target it. The only risk is receiving a misnamed file with a .fac extension that is actually a different format.
Format details
in a nutshell- Fractint Color Map - FAC extension was also used by older Fractint fractal software for color map/palette files - unrelated to the image format.
Programs that open FAC files
Windows2 apps
Converter Pro (Graphics Converter Pro)
Paid Open the file via File > Open; supports batch conversion of FAC files. 
macOS1 app
Linux3 apps
fromface
Open-source CLI tool: fromface file.fac > file.pbm converts FAC to PBM; part of old UNIX face utilities. Likely available in legacy package repos only.
Unix (general)
Built-in N/A as a distinct opener - 'Unix' is an OS, not a viewer. Remove from programs list. Technical details
deep spec| Encoding | Text header + ASCII hex-encoded binary pixel data |
| Color depth | 1-bit monochrome to 8-bit grayscale; original use case was 1-bit black-and-white face portraits |
| Typical dimensions | 64×96 pixels (standard portrait size); no hard maximum defined in the format |
| File header | ASCII key:value lines; mandatory fields include PicData: and Image:; optional personal info (name, email, institution) |
| Pixel storage order | Bottom-to-top scan lines, left-to-right within each line |
| Pixel encoding | ASCII hexadecimal (2 hex characters per byte); human-readable but space-inefficient |
| Typical file size | 2-10 KB |
| Magic bytes | None fixed; file begins with ASCII text header lines |
| Container | Plain text header followed by ASCII hex bitmap data - no binary container |
| Associated OS | Unix, Linux, BSD |
| Original use case | UNIX face-directory databases (fingerd), mailing-list user photo collections |
| Superseded by | PNG and JPEG for portrait storage; X-Face format for email-embedded face bitmaps |
| Released | circa 1985 (UNIX workstation era) |
| Specification | www.fileformat.info |
FAC conversions
Community Q&A
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